Variable-power optical system, optical device, and method for manufacturing variable-power optical system

ABSTRACT

Comprising a first lens group G 1  having positive refractive power, disposed at the most object side, and an image side lens group disposed at a side closer to an image than the first lens group G 1 , upon zooming, at least a distance between the first lens group G 1  and the image side lens group being varied, the image side lens group comprising a vibration reduction lens group GVR which is moved so as to have a component in a direction perpendicular to the optical axis and a focusing lens group GF which is moved along the optical axis upon focusing, thereby providing a variable magnification optical system which has a higher optical performance, an optical apparatus and a method for manufacturing a variable magnification optical system.

TECHNICAL FIELD

The present invention relates to a variable magnification opticalsystem, an optical device, and a method for producing the variablemagnification optical system.

BACKGROUND ART

Conventionally, there have been proposed variable magnification opticalsystems which are suitable for a photographing camera, an electronicstill camera, a video camera or the like. See, for example, Japanesepatent application Laid-Open Gazette No. 2013-105131.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese patent application Laid-Open Gazette No.2013-105131

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

However, in the conventional variable magnification optical systems asdescribed above, there was a problem that the optical performance wasinsufficient.

The present invention is made in view of the above-mentioned problem. Itis an object of the present invention to provide a variablemagnification optical system with higher optical performance, an opticalapparatus, and a method for manufacturing the variable magnificationoptical system.

Means for Solving the Problem

In order to solve the above-mentioned object, according to a firstaspect of the present invention, there is provided a variablemagnification optical system comprising:

a first lens group having positive refractive power, disposed at themost object side, and

an image side lens group disposed at a side closer to an image than thefirst lens group,

upon zooming, at least a distance between the first lens group and theimage side lens group being varied,

the image side lens group comprising a vibration reduction lens groupwhich is moved so as to have a component in a direction perpendicular tothe optical axis and a focusing lens group which is moved along theoptical axis upon focusing.

According to a second aspect of the present invention, there is provideda variable magnification optical system comprising:

a first lens group having positive refractive power, disposed at themost object side, and

an image side lens group disposed at a side closer to an image than thefirst lens group,

upon zooming, at least a distance between the first lens group and theimage side lens group being varied,

the image side lens group comprising a focusing lens group which ismoved along the optical axis upon focusing,

the focusing lens group comprising, in order from an object side, afirst focusing group and a second focusing group, and

the following conditional expression is satisfied:

0.10<|fp|/f4<0.45

where fp denotes a focal length of the second focusing group; and f4denotes a focal length of the image side lens group.

Further, in the first and the second aspects of the present invention,

upon zooming, the first lens group is preferably fixed for the position.

Further, in the first and the second aspects of the present invention,

it is preferable that the focusing lens group comprises a first focusinggroup having negative refractive power and a second focusing grouphaving positive refractive power, and

that, upon focusing, a distance between the first focusing group and thesecond focusing group is varied.

Further, in the first and the second aspects of the present invention,

it is preferable that the focusing lens group comprises a first focusinggroup and a second focusing group, and

that, upon focusing from an infinitely distance object to a closedistance object, the first focusing group is moved along the opticalaxis toward the image side and the second focusing group is moved alongthe optical axis toward the object side.

Further, in the first and the second aspects of the present invention,

it is preferable that the focusing lens group comprises a first focusinggroup having negative refractive power and a second focusing group, and

that the following conditional expression is satisfied:

0.20<(−fn)/f4<0.60

where fn denotes a focal length of the first focusing group; and f4denotes a focal length of the image side lens group.

Further, in the second aspect of the present invention,

it is preferable that the image side lens group comprises a vibrationreduction lens group which is moved so as to have a component in adirection perpendicular to the optical axis.

Further, in the first and the second aspects of the present invention,

it is preferable that the image side lens group comprises a vibrationreduction lens group which is moved so as to have a component in adirection perpendicular to the optical axis, and

that the following conditional expression is satisfied:

0.10<|fvr|/f4<0.80

where fvr denotes a focal length of the vibration reduction lens group,and f4 denotes a focal length of the image side lens group.

Further, in the first and the second aspects of the present invention,

it is preferable that the focusing lens group comprises a first focusinggroup and a second focusing group, and

that the following conditional expression is satisfied:

0.12<D/D4<0.40

where D denotes a distance between the first focusing group and thesecond focusing group upon focusing on an infinitely distant object, andD4 denotes a length on the optical axis of the image side lens group.

Further, in the first and the second aspects of the present invention,

it is preferable that the image side lens group is a lens group disposedat the most image side, and

that, upon zooming, a distance between the lenses included in the imageside lens group is not varied.

Further, the first and the second aspects of the present inventionpreferably comprise,

in order from an object side, the first lens group, a second lens grouphaving negative refractive power, a third lens group having positiverefractive power, and the image side lens group.

Further, a third aspect of the present invention provides

an optical apparatus equipped with the variable magnification opticalsystem according to the first aspect of the present invention.

Further, a fourth aspect of the present invention provides

an optical apparatus equipped with the variable magnification opticalsystem according to the second aspect of the present invention.

Further, a fifth aspect of the present invention provides

a method for manufacturing a variable magnification optical systemcomprising, in order from an object side, a first lens group havingpositive refractive power, a second lens group having negativerefractive power, a third lens group having positive refractive powerand a fourth lens group having positive refractive power, the methodcomprising:

configuring the lens groups such that, upon zooming, a distance betweenadjacent lens groups is varied,

constructing the fourth lens group so as to comprise a vibrationreduction lens group which is moved so as to have a component in adirection perpendicular to the optical axis and a focusing lens groupwhich is moved along the optical axis upon focusing.

Further, a sixth aspect of the present invention provides

a method for manufacturing a variable magnification optical systemcomprising, in order from an object side, a first lens group havingpositive refractive power, a second lens group having negativerefractive power, a third lens group having positive refractive powerand a fourth lens group having positive refractive power, the methodcomprising:

configuring the lens groups such that, upon zooming, a distance betweenadjacent lens groups is varied,

constructing the fourth lens group so as to comprise a focusing lensgroup which is moved along the optical axis upon focusing,

constructing the focusing lens group so as to comprise, in order from anobject side, a first focusing group having negative refractive power anda second focusing group having positive refractive power, and

constructing the variable magnification optical system so as to satisfythe following conditional expression:

0.10<fp/f4<0.45

where fp denotes a focal length of the second focusing group; and f4denotes a focal length of the fourth lens group.

Effect of the Invention

According to the first, the third and the fifth aspects of the presentinvention, a variable magnification optical system with higher opticalperformance while having a vibration reducing function, an opticalapparatus, and a method for manufacturing the variable magnificationoptical system can be provided.

According to the second, the fourth and the sixth aspects of the presentinvention, a variable magnification optical system with higher opticalperformance, an optical apparatus, and a method for manufacturing thevariable magnification optical system can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional view of a variable magnification optical systemin a wide-angle end state according to a first Example common to a firstand a second Embodiment of the present application.

FIGS. 2A and 2B are graphs showing various aberrations of the variablemagnification optical system according to the first Example of thepresent application in a wide-angle end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 2C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIGS. 3A and 3B are graphs showing various aberrations of the variablemagnification optical system according to the first Example of thepresent application in an intermediate focal length state, upon focusingon an infinitely distant object, and upon focusing on a close distanceobject, respectively, and FIG. 3C is a graph showing a coma aberrationof the variable magnification optical system when the vibrationreduction is conducted upon focusing on an infinitely distant object.

FIGS. 4A and 4B are graphs showing various aberrations of the variablemagnification optical system according to the first Example of thepresent application in a telephoto end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 4C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIG. 5 shows a sectional view of a variable magnification optical systemin a wide-angle end state according to a second Example common to thefirst and the second Embodiments of the present application.

FIGS. 6A and 6B are graphs showing various aberrations of the variablemagnification optical system according to the second Example of thepresent application in a wide-angle end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 6C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIGS. 7A and 7B are graphs showing various aberrations of the variablemagnification optical system according to the second Example of thepresent application in an intermediate focal length state, upon focusingon an infinitely distant object, and upon focusing on a close distanceobject, respectively, and FIG. 7C is a graph showing a coma aberrationof the variable magnification optical system when the vibrationreduction is conducted upon focusing on an infinitely distant object.

FIGS. 8A and 8B are graphs showing various aberrations of the variablemagnification optical system according to the second Example of thepresent application in a telephoto end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 8C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIG. 9 shows a sectional view of a variable magnification optical systemin a wide-angle end state according to a third Example common to thefirst and the second Embodiments of the present application.

FIGS. 10A and 10B are graphs showing various aberrations of the variablemagnification optical system according to the third Example of thepresent application in a wide-angle end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 10C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIGS. 11A and 11B are graphs showing various aberrations of the variablemagnification optical system according to the third Example of thepresent application in an intermediate focal length state, upon focusingon an infinitely distant object, and upon focusing on a close distanceobject, respectively, and FIG. 11C is a graph showing a coma aberrationof the variable magnification optical system when the vibrationreduction is conducted upon focusing on an infinitely distant object.

FIGS. 12A and 12B are graphs showing various aberrations of the variablemagnification optical system according to the third Example of thepresent application in a telephoto end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 12C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIG. 13 is a view showing a configuration of a camera equipped with thevariable magnification optical systems according to the first and thesecond Embodiments of the present application.

FIG. 14 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system according to the firstEmbodiment of the present application.

FIG. 15 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system according to the secondEmbodiment of the present application.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Now, a variable magnification optical system according to a firstEmbodiment of the present application, an optical apparatus, and amethod for producing the variable magnification optical system will bedescribed below.

A variable magnification optical system according to a first Embodimentof the present application is characterized in that the systemcomprises, in order from an object side, a first lens group havingpositive refractive power, a second lens group having negativerefractive power, a third lens group having positive refractive powerand a fourth lens group having positive refractive power, and uponzooming, a distance between adjacent lens groups is varied, and thefirst lens group is fixed for the position, and the fourth lens groupcomprises a vibration reduction lens group which is moved so as to havea component in a direction perpendicular to the optical axis and afocusing lens group which is moved along the optical axis upon focusing.

As described above, the variable magnification optical system accordingto the first Embodiment of the present application comprises, in orderfrom an object side, a first lens group having positive refractivepower, a second lens group having negative refractive power, a thirdlens group having positive refractive power and a fourth lens grouphaving positive refractive power. Upon zooming, the distance between theadjacent lens groups is varied, and the first lens group is fixed forthe position. With the configuration, it is possible to achieve ensuringa desired variable magnification ratio, simplifying a variablemagnification mechanism, downsizing a lens barrel and reducingperformance degradation due to a manufacturing error.

Also, as described above, the variable magnification optical systemaccording to the first Embodiment of the present application isconstructed so that the fourth lens group comprises the focusing lensgroup which is moved along the optical axis upon focusing. With theconfiguration, it is possible to achieve reducing a change in theoptical performance upon focusing and downsizing a focusing unit.

Also, as described above, the variable magnification optical systemaccording to the first Embodiment of the present application isconstructed so that the fourth lens group comprises a vibrationreduction lens group which is moved so as to have a component in adirection perpendicular to the optical axis. With the configuration, itis possible to achieve correcting image blur caused by camera shake orvibration, i.e., implementing vibration reduction, in particular,reducing a change in the optical performance upon the vibrationreduction, and downsizing a vibration reduction unit.

With the above described configuration, it is possible to realize avariable magnification optical system which has higher opticalperformance while exhibiting the vibration reduction function.

It is also desirable that the variable magnification optical systemaccording to the first embodiment of the present application satisfiesthe following conditional expression (1-1):

0.10<|fvr|/f4<0.80  (1-1)

where fvr denotes a focal length of the vibration reduction lens group,and f4 denotes a focal length of the fourth lens group.

The conditional expression (1-1) defines a range of the focal length ofthe vibration reduction lens group relative to the focal length of thefourth lens group. The variable magnification optical system accordingto the first Embodiment of the present application can achieve goodperformance for vibration reduction by satisfying the followingconditional expression (1-1).

When the value of |fvr|/f4 is equal to or falls below the lower limit ofthe conditional expression (1-1) for the variable magnification opticalsystem according to the first Embodiment of the present application, itis not preferred because the vibration reduction lens group becomeslarger in the refractive power, and as a result, it is difficult to makea correction of image plane variation upon vibration reduction and ofeccentric coma. Note that, in order to further ensure the advantageouseffect of the present application, the lower limit value of theconditional expression (1-1) is more preferably set to 0.20.

When the value of |fvr|/f4 is equal to or exceeds the upper limit of theconditional expression (1-1) for the variable magnification opticalsystem according to the first Embodiment of the present application, itis not preferred because the vibration reduction lens group becomessmaller in the refractive power, and as a result, it is difficult todownsize the vibration reduction unit. Note that, in order to furtherensure the advantageous effect of the present application, the upperlimit value of the conditional expression (1-1) is more preferably setto 0.60.

Also, the variable magnification optical system according to the firstEmbodiment of the present application is preferably constructed so thatthe focusing lens group comprises, in order from the object side, afirst focusing group having negative refractive power and a secondfocusing group having positive refractive power, and upon focusing froman infinitely distant object to a close distant object, the firstfocusing group is moved toward the image side along the optical axis,and the second focusing group is moved toward the object side along theoptical axis. With the configuration, it is possible to achieve reducinga change in the optical performance due to the focusing.

It is also desirable that the variable magnification optical systemaccording to the first Embodiment of the present application satisfiesthe following conditional expression (1-2):

0.10<(−fn)/f4<0.60  (1-2)

where fn denotes a focal length of the first focusing group; and f4denotes a focal length of the fourth lens group.

The conditional expression (1-2) defines a range of the focal length ofthe first focusing group relative to the focal length of the fourth lensgroup. The variable magnification optical system according to the firstEmbodiment of the present application can achieve good opticalperformance upon focusing by satisfying the conditional expression(1-2).

When the value of (−fn)/f4 is equal to or falls below the lower limit ofthe conditional expression (1-2) for the variable magnification opticalsystem according to the first Embodiment of the present application, itis not preferred because the first focusing group becomes larger in therefractive power, and as a result, it is difficult to make a correctionof spherical aberration and curvature of field upon focusing. Note that,in order to further ensure the advantageous effect of the presentapplication, the lower limit value of the conditional expression (1-2)is more preferably set to 0.22.

On the other hand, when the value of (−fn)/f4 is equal to or exceeds theupper limit of the conditional expression (1-2) for the variablemagnification optical system according to the first Embodiment of thepresent application, it is not preferred because the fourth lens groupbecomes larger in the refractive power, and as a result, it is difficultto make a correction of spherical aberration in the telephoto end state.Note that, in order to further ensure the advantageous effect of thepresent application, the upper limit value of the conditional expression(1-2) is more preferably set to 0.45.

It is also desirable that the variable magnification optical systemaccording to the first Embodiment of the present application satisfiesthe following conditional expression (1-3):

0.10<fp/f4<0.50  (1-3)

where fp denotes a focal length of the second focusing group; and f4denotes a focal length of the fourth lens group.

The conditional expression (1-3) defines a range of the focal length ofthe second focusing group relative to the focal length of the fourthlens group. The variable magnification optical system according to thefirst Embodiment of the present application can achieve good opticalperformance upon focusing by satisfying the conditional expression(1-3).

When the value of fp/f4 is equal to or falls below the lower limit ofthe conditional expression (1-3) for the variable magnification opticalsystem according to the first Embodiment of the present application, itis not preferred because the second focusing group becomes larger in therefractive power, and as a result, a variation in aberration uponfocusing becomes larger. Note that, in order to further ensure theadvantageous effect of the present application, the lower limit value ofthe conditional expression (1-3) is more preferably set to 0.15.

On the other hand, when the value of fp/f4 is equal to or exceeds theupper limit of the conditional expression (1-3) for the variablemagnification optical system according to the first Embodiment of thepresent application, it is not preferred because the fourth lens groupbecomes larger in the refractive power, and as a result, it is difficultto make a correction of spherical aberration in the telephoto end state.Note that, in order to further ensure the advantageous effect of thepresent application, the upper limit value of the conditional expression(1-3) is more preferably set to 0.40.

It is also desirable that the variable magnification optical systemaccording to the first Embodiment of the present application satisfiesthe following conditional expression (1-4):

0.12<D/D4<0.40  (1-4)

where D denotes a distance between the first focusing group and thesecond focusing group upon focusing on an infinitely distant object, andD4 denotes a length on the optical axis of the fourth lens group.

The conditional expression (1-4) defines an air distance between thefirst focusing group and the second focusing group relative to athickness of, that is, a length on the optical axis of the fourth lensgroup. The variable magnification optical system according to the firstEmbodiment of the present application can achieve good opticalperformance upon focusing by satisfying the conditional expression(1-4).

When the value of D/D4 is equal to or falls below the lower limit of theconditional expression (1-4) for the variable magnification opticalsystem according to the first Embodiment of the present application, asufficient space cannot be disadvantageously ensured for the movement ofthe first focusing group and the second focusing group upon focusing.Owing to this, the refractive power of the first focusing group and thesecond focusing group has to be made larger, and as a result, it isdifficult to make a correction of spherical aberration and curvature offield upon focusing, which is not preferred. Note that, in order tofurther ensure the advantageous effect of the present application, thelower limit value of the conditional expression (1-4) is more preferablyset to 0.15.

On the other hand, when the value of D/D4 is equal to or exceeds theupper limit of the conditional expression (1-4) for the variablemagnification optical system according to the first Embodiment of thepresent application, a sufficient space for the disposition of thevibration reduction lens group cannot be disadvantageously ensuredwithin the fourth lens group. When the refractive power of the firstlens group and the second lens group is made greater in order to ensurethe space for the disposition of the vibration reduction lens groupwithin the fourth lens group, however, it is difficult to make acorrection of the spherical aberration in the telephoto end state, whichis not preferred. Note that, in order to further ensure the advantageouseffect of the present application, the upper limit value of theconditional expression (1-4) is more preferably set to 0.35.

In the variable magnification optical system according to the firstEmbodiment of the present application, it is desired that the vibrationreduction lens group is disposed at the side closer to the image thanthe focusing lens group. With such configuration, it is possible to makethe diameter of the vibration reduction lens group smaller and thusachieve downsizing the lens barrel.

An optical apparatus of the present application is characterized bycomprising a variable magnification optical system of theabove-mentioned configuration according to the first Embodiment.Accordingly, an optical apparatus can be realized which is provided witha higher optical performance while fulfilling the vibration reductionfunction.

A method for manufacturing a variable magnification optical systemaccording to the first Embodiment of the present application ischaracterized in that the method is a method for manufacturing avariable magnification optical system comprising, in order from anobject side, a first lens group having positive refractive power, asecond lens group having negative refractive power, a third lens grouphaving positive refractive power, and a fourth lens group havingpositive refractive power, and the method comprises configuring the lensgroups such that, upon zooming, a distance between adjacent lens groupsis varied and the position of the first lens group is fixed, andconstructing the fourth lens group so as to comprise a vibrationreduction lens group which is moved so as to contain a component in adirection perpendicular to the optical axis and a focusing lens groupwhich is moved along the optical axis upon focusing. With the method, itis possible to manufacture a variable magnification optical system whichhas higher optical performance while exhibiting the vibration reductionfunction.

Now, a variable magnification optical system according to a secondEmbodiment of the present application, an optical apparatus, and amethod for producing the variable magnification optical system will bedescribed below.

The variable magnification optical system according to the secondEmbodiment of the present application is characterized in that thesystem comprises, in order from an object side, a first lens grouphaving positive refractive power, a second lens group having negativerefractive power, a third lens group having positive refractive powerand a fourth lens group having positive refractive power, and uponzooming, a distance between adjacent lens groups is varied, and thefirst lens group is fixed for the position, and the fourth lens groupcomprises a focusing lens group which is moved along the optical axisupon focusing, the focusing lens group comprises, in order from objectside, a first focusing group having negative refractive power and asecond focusing group having positive refractive power, and the systemsatisfies the following conditional expression:

0.10<fp/f4<0.45  (2-1)

where fp denotes a focal length of the second focusing group; and f4denotes a focal length of the fourth lens group.

As described above, the variable magnification optical system accordingto the second Embodiment of the present application comprises, in orderfrom an object side, a first lens group having positive refractivepower, a second lens group having negative refractive power, a thirdlens group having positive refractive power and a fourth lens grouphaving positive refractive power. Upon zooming, the distance between theadjacent lens groups is varied, and the first lens group is fixed forthe position. With the configuration, it is possible to achieve ensuringa desired variable magnification ratio, simplifying a variablemagnification mechanism, downsizing a lens barrel and reducingperformance degradation due to a manufacturing error.

Also, as described above, the variable magnification optical systemaccording to the second Embodiment of the present application isconstructed so that the fourth lens group comprises the focusing lensgroup which is moved along the optical axis upon focusing. With theconfiguration, it is possible to achieve reducing a change in theoptical performance upon focusing and downsizing a focusing unit.

Also, as described above, the variable magnification optical systemaccording to the second Embodiment of the present application isconstructed so that the focusing lens group comprises, in order from theobject side, a first focusing group having negative refractive power anda second focusing having positive refractive power. With theconfiguration, it is possible to reduce a change in the opticalperformance due to the focusing.

The conditional expression (2-1) defines a range of the focal length ofthe second focusing group relative to the focal length of the fourthlens group. The variable magnification optical system according to thesecond Embodiment of the present application can achieve good opticalperformance upon focusing by satisfying the conditional expression(2-1).

When the value of fp/f4 is equal to or falls below the lower limit ofthe conditional expression (2-1) for the variable magnification opticalsystem according to the second Embodiment of the present application, itis not preferred because the second focusing group becomes larger in therefractive power, and as a result, a variation in aberration uponfocusing becomes larger. Note that, in order to further ensure theadvantageous effect of the present application, the lower limit value ofthe conditional expression (2-1) is more preferably set to 0.15.

On the other hand, when the value of fp/f4 is equal to or exceeds theupper limit of the conditional expression (2-1) for the variablemagnification optical system according to the second Embodiment of thepresent application, it is not preferred because the fourth lens groupbecomes larger in the refractive power, and as a result, it is difficultto make a correction of spherical aberration in the telephoto end state.Note that, in order to further ensure the advantageous effect of thepresent application, the upper limit value of the conditional expression(2-1) is more preferably set to 0.40.

With the above described configuration, it is possible to realize avariable magnification optical system which is provided with higheroptical performance.

Also, the variable magnification optical system according to the secondEmbodiment of the present application is preferably constructed so that,upon focusing from an infinitely distant object to a close distantobject, the first focusing group is moved toward the image side alongthe optical axis, and the second focusing group is moved toward theobject side along the optical axis. With the configuration, it ispossible to satisfactorily reduce a change in the optical performancedue to the focusing.

It is also desirable that the variable magnification optical systemaccording to the second Embodiment of the present application satisfiesthe following conditional expression (2-2):

0.20<(−fn)/f4<0.60  (2-2)

where fn denotes a focal length of the first focusing group; and f4denotes a focal length of the fourth lens group.

The conditional expression (2-2) defines a range of the focal length ofthe first focusing group relative to the focal length of the fourth lensgroup. The variable magnification optical system according to the secondEmbodiment of the present application can achieve good opticalperformance upon focusing by satisfying the conditional expression(2-2).

When the value of (−fn)/f4 is equal to or falls below the lower limit ofthe conditional expression (2-2) for the variable magnification opticalsystem according to the second Embodiment of the present application, itis not preferred because the first focusing group becomes larger in therefractive power, and as a result, it is difficult to make a correctionof spherical aberration and curvature of field upon focusing. Note that,in order to further ensure the advantageous effect of the presentapplication, the lower limit value of the conditional expression (2-2)is more preferably set to 0.22.

On the other hand, when the value of (−fn)/f4 is equal to or exceeds theupper limit of the conditional expression (2-2) for the variablemagnification optical system according to the second Embodiment of thepresent application, it is not preferred because the fourth lens groupbecomes larger in the refractive power, and as a result, it is difficultto make a correction of spherical aberration in the telephoto end state.Note that, in order to further ensure the advantageous effect of thepresent application, the upper limit value of the conditional expression(2-2) is more preferably set to 0.45.

Also, the variable magnification optical system according to the secondEmbodiment of the present application is preferably constructed so thatthe fourth lens group comprises the vibration reduction lens group whichis moved so as to have a component in a direction perpendicular to theoptical axis. With the configuration, it is possible to achievecorrecting image blur caused by camera shake or vibration, i.e.,implementing vibration reduction, in particular, reducing a change inthe optical performance upon the vibration reduction, and downsizing avibration reduction unit.

It is also desirable that the variable magnification optical systemaccording to the second Embodiment of the present application satisfiesthe following conditional expression (2-3):

0.10<|fvr|/f4<0.80  (2-3)

where fvr denotes a focal length of the vibration reduction lens group,and f4 denotes a focal length of the fourth lens group.

The conditional expression (2-3) defines a range of the focal length ofthe vibration reduction lens group relative to the focal length of thefourth lens group. The variable magnification optical system accordingto the second Embodiment of the present application can achieve goodperformance for vibration reduction by satisfying the followingconditional expression (2-3).

When the value of |fvr|/f4 is equal to or falls below the lower limit ofthe conditional expression (2-3) for the variable magnification opticalsystem according to the second Embodiment of the present application, itis not preferred because the vibration reduction lens group becomeslarger in the refractive power, and as a result, it is difficult to makea correction of image plane variation upon vibration reduction and ofeccentric coma. Note that, in order to further ensure the advantageouseffect of the present application, the lower limit value of theconditional expression (2-3) is more preferably set to 0.20.

On the other hand, when the value of |fvr|/f4 is equal to or exceeds theupper limit of the conditional expression (2-3) for the variablemagnification optical system according to the second Embodiment of thepresent application, it is not preferred because the vibration reductionlens group becomes smaller in the refractive power, and as a result, itis difficult to downsize the vibration reduction unit. Note that, inorder to further ensure the advantageous effect of the presentapplication, the upper limit value of the conditional expression (2-3)is more preferably set to 0.60.

Also, the variable magnification optical system according to the secondEmbodiment of the present application is preferably constructed so thatthe vibration reduction lens is disposed at the side closer to the imagethan the focusing lens group. With such configuration, it is possible tomake the diameter of the vibration reduction lens group smaller andachieve downsizing the lens barrel.

It is also desirable that the variable magnification optical systemaccording to the second Embodiment of the present application satisfiesthe following conditional expression (2-4):

0.12<D/D4<0.40  (2-4)

where D denotes a distance between the first focusing group and thesecond focusing group upon focusing on an infinitely distant object, andD4 denotes a length on the optical axis of the fourth lens group.

The conditional expression (2-4) defines an air distance between thefirst focusing group and the second focusing group relative to athickness of the fourth lens group, that is, a length on the opticalaxis of the fourth lens group. The variable magnification optical systemaccording to the second Embodiment of the present application canachieve good optical performance upon focusing by satisfying theconditional expression (2-4).

When the value of D/D4 is equal to or falls below the lower limit of theconditional expression (2-4) for the variable magnification opticalsystem according to the second Embodiment of the present application, asufficient space cannot be disadvantageously ensured for the movement ofthe first focusing group and the second focusing group upon focusing.Owing to this, however, the refractive power of the first focusing groupand the second focusing group has to be made larger, and as a result, itis difficult to make a correction of spherical aberration and of fieldcurvature upon focusing, which is not preferred. Note that, in order tofurther ensure the advantageous effect of the present application, thelower limit value of the conditional expression (2-4) is more preferablyset to 0.15.

On the other hand, when the value of D/D4 is equal to or exceeds theupper limit of the conditional expression (2-4) for the variablemagnification optical system according to the second Embodiment of thepresent application, a sufficient space for the disposition of thevibration reduction lens group cannot be disadvantageously ensuredwithin the fourth lens group. When the refractive power of the firstlens group and the second lens group is made greater in order to ensurethe space for the disposition of the vibration reduction lens groupwithin the fourth lens group, however, it is difficult to make acorrection of the spherical aberration in the telephoto end state, whichis not preferred. Note that, in order to further ensure the advantageouseffect of the present application, the upper limit value of theconditional expression (2-4) is more preferably set to 0.35.

An optical apparatus of the present application is characterized bycomprising a variable magnification optical system of theabove-mentioned configuration according to the second Embodiment. As aresult, it is possible to realize an optical apparatus with higheroptical performance.

A method for manufacturing a variable magnification optical systemaccording to the second Embodiment of the present application ischaracterized in that the method is a method for manufacturing avariable magnification optical system comprising, in order from anobject side, a first lens group having positive refractive power, asecond lens group having negative refractive power, a third lens grouphaving positive refractive power, and a fourth lens group havingpositive refractive power, and the method comprises configuring the lensgroups such that, upon zooming, a distance between adjacent lens groupsis varied and the position of the first lens group is fixed,constructing the fourth lens group so as to comprise a focusing lensgroup which is moved along the optical axis upon focusing, constructingthe focusing lens group so as to comprise, in order from the objectside, a first focusing group having negative refractive power and asecond focusing group having positive refractive power, and constructingthe variable magnification optical system so as to satisfy the followingconditional expression (2-1). With the method, it is possible tomanufacture a variable magnification optical system with higher opticalperformance.

0.10<fp/f4<0.45  (2-1)

where fp denotes a focal length of the second focusing group; and f4denotes a focal length of the fourth lens group.

Now, variable magnification optical systems according to numericalExamples of the first and the second Embodiments of the presentapplication will be described below with reference to the accompanyingdrawings. In this connection, a first to third Examples are common tothe first and the second Embodiments.

First Example

FIG. 1 shows a sectional view of a variable magnification optical systemin a wide-angle end state according to a first Example common to thefirst and the second Embodiments of the present application. In FIG. 1,and FIGS. 5 and 9, the arrows refer to the movement locus of lens groupsupon zooming from a wide-angle end state (W) to a telephoto end state(T).

The variable magnification optical system according to the presentExample is composed of, in order from the object side, a first lensgroup G1 having positive refractive power, a second lens group G2 havingnegative refractive power, a third lens group G3 having positiverefractive power, and a fourth lens group G4 having positive refractivepower.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L101 having aconvex surface facing the object side cemented with a positive meniscuslens L102 having a convex surface facing the object side, and a positivemeniscus lens L103 having a convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented lens constructed by a double convex positive lens L201 cementedwith a double concave negative lens L202, a negative meniscus lens L203lens having a convex surface facing the object side, a positive meniscuslens L204 having a convex surface facing the object side, and a negativemeniscus lens L205 having a convex surface facing the image side.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a double convex positive lens L301 cementedwith a negative meniscus lens L302 having a convex surface facing theimage side.

The fourth lens group G4 consists of, in order from the object side, afirst fixed lens group G41 having positive refractive power, a focusinglens group GF having positive refractive power, and a second fixed lensgroup G42 having negative refractive power.

The first fixed lens group G41 consists of, in order from the objectside, an aperture stop S, a double convex positive lens L401, and acemented lens constructed by a double convex positive lens L402 cementedwith a double concave negative lens L403.

The focusing lens group GF consists of, in order from the object side, afirst focusing group GN having negative refractive power and a secondfocusing group GP having positive refractive power.

The first focusing group GN consists of, in order from the object side,a double concave negative lens L404, and a cemented lens constructed bya double concave negative lens L405 cemented with a double convexpositive lens L406.

The second focusing group GP consists of, in order from the object side,a positive meniscus lens L407 having a convex surface facing the objectside, a cemented lens constructed by a negative meniscus lens L408having a convex surface facing the object side cemented with and adouble convex positive lens L409, and a positive meniscus lens L410having a convex surface facing the object side.

The second fixed lens group G42 consists of, in order from the objectside, a negative meniscus lens L411 having a convex surface facing theobject side, a vibration reduction lens group GVR having negativerefractive power, a positive meniscus lens L414 having a convex surfacefacing the object side, a negative meniscus lens L415 having a convexsurface facing the image side, and a double convex positive lens L416.

The vibration reduction lens group GVR consists of, in order from theobject side, a cemented lens constructed by a double convex positivelens L412 cemented with a double concave negative lens L413.

In the variable magnification optical system according to the presentexample with the above configuration, upon zooming from a wide angle endstate to a telephoto end state, the second lens group G2 and the thirdlens group G3 are moved toward the image side along the optical axissuch that an air distance between the first lens group G1 and the secondlens group G2 is increased, an air distance between the second lensgroup G2 and the third lens group G3 is varied, and an air distancebetween the third lens group G3 and the fourth lens group G4 is varied.In this case, the first lens group G1 and the fourth lens group G4 arefixed for their positions.

In the variable magnification optical system according to the presentexample, the first focusing group GN in the fourth lens group G4 ismoved along the optical axis toward the image side and the secondfocusing group GP is moved along the optical axis toward the object sideto thereby conduct focusing from an infinite distance object to a closedistance object.

Also, in the variable magnification optical system according to thepresent example, the vibration reduction lens group GVR in the fourthlens group G4 is moved so as to have a component in a directionperpendicular to the optical axis to thereby conduct the vibrationreduction.

Values of specifications for the variable magnification optical systemaccording to the present example are shown in Table 1 given below.

Table 1, the f denotes a focal length, and BF denotes a back focallength (a distance on the optical axis from the most image side lenssurface to the image plane I).

In [Surface Data], Surface number denotes an order of an optical surfacecounted from the object side, r denotes a radius of curvature, d denotesa surface-to-surface distance (a distance between an n-th surface and an(n+1)-th surface, where n is an integer), nd denotes refractive indexfor d-line (wavelength: 587.6 nm) and vd denotes an Abbe number ford-line (wavelength: 587.6 nm). Further, Object surface denotes an objectsurface, and Variable denotes a variable surface-to-surface distance.Also, Stop S denotes an aperture stop S, Image plane denotes an imageplane I. Meanwhile, radius of curvature r=∞ denotes a plane surface.Refractive index of air nd=1.000000 is omitted.

In [Various Data], FNO denotes an F-number, ω denotes a half angle ofview (in a unit of degree “°”), Y denotes an image height, TL denotes atotal length of the variable magnification optical system according tothe present example (that is, a distance on the optical axis from thefirst surface of lens surface to the image plane I), and do denotes avariable distance between the n-th surface and the (n+1)th surface. Inaddition, W, M and T denote the wide-angle end state, intermediate focallength state and telephoto end state, respectively.

In [Lens Group Data], there are shown a starting surface number and afocal length of each lens group.

In [Values for Conditional Expressions] are shown values correspondingto the conditional expressions for the variable magnification opticalsystem according to the present example.

It is noted, here, that “mm” is generally used as the unit of a length,such as the focal length f, the radius of curvature r, and the likeshown in Table 1. However, since similar optical performance can beobtained by an optical system which is proportionally enlarged orreduced for its dimension, the unit is not necessarily limited to “mm”.

The reference symbols in Table 1 described above are also used in Tablesfor each of the Examples provided later in the same way.

TABLE 1 First Example [Surface Data] Surface number r d nd νd Objectsurface ∞  1 89.536 1.200 1.761820 26.58  2 64.499 9.366 1.497820 82.57 3 492.821 0.100  4 75.862 6.550 1.497820 82.57  5 264.546 Variable  6126.389 4.319 1.846660 23.80  7 −94.375 1.200 1.617720 49.81  8 25.6343.792  9 231.776 1.200 1.902650 35.72 10 46.195 4.729 11 39.709 3.2691.805180 25.45 12 159.426 2.773 13 −37.627 1.200 1.883000 40.66 14−110.363 Variable 15 1669.225 5.089 1.816000 46.59 16 −27.674 1.2001.950000 29.37 17 −57.219 Variable 18(Stop S) ∞ 0.100 19 128.237 3.4981.883000 40.66 20 −84.529 0.200 21 38.419 5.579 1.518600 69.89 22−52.514 1.200 1.902000 25.26 23 574.136 Variable 24 −100.148 1.2001.902650 35.72 25 38.967 2.586 26 −70.460 1.200 1.749500 35.25 27 23.9455.990 1.805180 25.45 28 −51.890 Variable 29 33.327 3.074 1.693500 53.2030 119.457 0.100 31 104.887 1.200 1.950000 29.37 32 24.444 5.2091.516800 63.88 33 −46.867 0.100 34 37.520 2.904 1.640000 60.19 35224.916 Variable 36 30.011 1.200 1.883000 40.66 37 18.287 4.085 3876.702 3.755 1.846660 23.80 39 −23.239 1.200 1.883000 40.66 40 28.6355.759 41 35.576 2.746 1.487490 70.32 42 81.503 3.814 43 −27.066 1.2001.883000 40.66 44 −67.449 0.100 45 51.239 3.982 1.719990 50.27 46−496.232 BF Image plane ∞ [Various Data] Variable magnification ratio(zoom ratio) 2.75 W M T f 71.4 140.0 196.0 FNO 4.1 4.1 4.1 ω 17.0° 8.7°6.2° Y 21.6 21.6 21.6 TL 219.319 219.319 219.319 BF 37.319 37.319 37.319<Infinite focusing state> W M T d5 1.000 37.026 47.716 d14 24.799 11.6901.000 d17 23.916 1.000 1.000 d23 1.770 1.770 1.770 d28 21.537 21.53721.537 d35 1.000 1.000 1.000 <Close distance focusing state(photographic distance 0.36 m)> W M T d5 1.000 37.026 47.716 d14 24.79911.690 1.000 d17 23.916 1.000 1.000 d23 3.564 6.906 12.167 d28 17.94911.266 0.743 d35 2.794 6.136 11.397 [Lens Group data] Group Startingsurface f 1 1 123.989 2 6 −31.623 3 15 81.447 4 18 109.876 [Values forConditional Expressions] (1-1) |fvr|/f4 = 0.45 (1-2) (−fn)/f4 = 0.42(1-3) fp/f4 = 0.30 (1-4) D/D4 = 0.25 (2-1) fp/f4 = 0.30 (2-2) (−fn)/f4 =0.42 (2-3) |fvr|/f4 = 0.45 (2-4) D/D4 = 0.25

FIGS. 2A and 2B are graphs showing various aberrations of the variablemagnification optical system according to the first Example of thepresent application in a wide-angle end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 2C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIGS. 3A and 3B are graphs showing various aberrations of the variablemagnification optical system according to the first Example of thepresent application in an intermediate focal length state, upon focusingon an infinitely distant object, and upon focusing on a close distanceobject, respectively, and FIG. 3C is a graph showing a coma aberrationof the variable magnification optical system when the vibrationreduction is conducted upon focusing on an infinitely distant object.

FIGS. 4A and 4B are graphs showing various aberrations of the variablemagnification optical system according to the first Example of thepresent application in a telephoto end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 4C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

In the aberration graphs, FNO denotes an F-number, NA denotes anumerical aperture, A denotes a half angle of view (in degree “°”), andH0 denotes an object height. More particularly, in the graphs ofspherical aberration are shown values for the F-number FNO,corresponding to the maximum aperture, or values of the numericalaperture NA. In the graphs of astigmatism and distortion are shownmaximum values for the half angle of view A or the object height H0. Inthe graphs of coma are shown values for the half angles of view A or theobject heights H0. In the graphs, d denotes an aberration curve atd-line (wavelength: 587.6 nm), and g denotes an aberration curve atg-line (wavelength: 435.8 nm). In the astigmatism graphs, the solid lineindicates a sagittal image plane, and the broken line indicates ameridional image plane. In the graphs of coma are shown coma aberrationsfor the half angles of view A or the object heights H0. Incidentally,the same symbols as in the present example are used also in variousaberration graphs in each of the Examples given later.

As is seen from the aberration graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance over the range from the wide-angle end state to thetelephoto end state and exhibits excellent optical performance also whenthe vibration reduction is conducted.

Second Example

FIG. 5 shows a sectional view of a variable magnification optical systemin a wide-angle end state according to a second Example common to thefirst and the second Embodiments of the present application.

The variable magnification optical system according to the presentexample is composed of, in order from the object side, a first lensgroup G1 having positive refractive power, a second lens group G2 havingnegative refractive power, a third lens group G3 having positiverefractive power, and a fourth lens group G4 having positive refractivepower.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L101 having aconvex surface facing the object side cemented with a double convexpositive lens L102, and a positive meniscus lens L103 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L201 having a convex surface facing the objectside, a cemented lens constructed by a double concave negative lens L202cemented with a double convex positive lens L203, and a negativemeniscus lens L204 having a convex surface facing the image side.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L301 having aconvex surface facing the object side cemented with a double convexpositive lens L302.

The fourth lens group G4 consists of, in order from the object side, afirst fixed lens group G41 having positive refractive power, a focusinglens group GF having positive refractive power, and a second fixed lensgroup G42 having negative refractive power.

The first fixed lens group G41 consists of, in order from the objectside, a double convex positive lens L401, an aperture stop S, a positivemeniscus lens L402 having a convex surface facing the object side, and apositive meniscus lens L403 having a convex surface facing the objectside.

The focusing lens group GF consists of, in order from the object side, afirst focusing group GN having negative refractive power and a secondfocusing group GP having positive refractive power.

The first focusing group GN consists of, in order from the object side,a cemented lens constructed by a double concave negative lens L404cemented with a positive meniscus lens L405 having a convex surfacefacing the object side.

The second focusing group GP consists of, in order from the object side,a cemented lens constructed by a negative meniscus lens L406 having aconvex surface facing the object side cemented with a double convexpositive lens L407, a double convex positive lens L408, and a doubleconvex positive lens L409.

The second fixed lens group G42 consists of, in order from the objectside, a negative meniscus lens L410 having a convex surface facing theobject side, a vibration reduction lens group GVR having negativerefractive power, a negative meniscus lens L413 having a convex surfacefacing the image side, a double convex positive lens L414, a negativemeniscus lens L415 having a convex surface facing the image side, and adouble convex positive lens L416.

The vibration reduction lens group GVR consists of, in order from theobject side, a cemented lens constructed by a negative meniscus lensL411 having a convex surface facing the object side cemented with apositive meniscus lens L412 having a convex surface facing the objectside.

In the variable magnification optical system according to the presentexample with the above configuration, upon zooming from a wide angle endstate to a telephoto end state, the second lens group G2 and the thirdlens group G3 are moved toward the image side along the optical axissuch that an air distance between the first lens group G1 and the secondlens group G2 is increased, an air distance between the second lensgroup G2 and the third lens group G3 is varied, and an air distancebetween the third lens group G3 and the fourth lens group G4 is varied.At that time, the first lens group G1 and the fourth lens group G4 arefixed for their positions.

In the variable magnification optical system according to the presentexample, the first focusing group GN in the fourth lens group G4 ismoved along the optical axis toward the image side and the secondfocusing group GP is moved along the optical axis toward the object sideto thereby conduct focusing from an infinitely distance object to aclose distance object.

Also, in the variable magnification optical system according to thepresent example, the vibration reduction lens group GVR in the fourthlens group G4 is moved so as to contain a component in a directionperpendicular to the optical axis to thereby conduct the vibrationreduction.

Values of specifications for the variable magnification optical systemaccording to the present example are shown in Table 2 given below.

TABLE 2 Second Example [Surface Data] Surface number r d nd νd Objectsurface ∞  1 87.518 1.200 1.846660 23.80  2 65.375 11.303  1.43384895.23  3 −521.284 0.100  4 69.096 7.026 1.497820 82.57  5 259.776Variable  6 92.515 1.200 1.883000 40.66  7 29.776 5.926  8 −92.500 1.2001.516800 63.88  9 31.244 5.682 1.846660 23.80 10 −1012.688 14.564  11−44.515 1.200 1.950000 29.37 12 −127.638 Variable 13 99.131 1.2001.950000 29.37 14 41.603 5.065 1.677900 50.67 15 −88.036 Variable 16184.530 2.883 1.497820 82.57 17 −127.449 0.100 18(Stop S) ∞ 0.100 1968.409 2.965 1.497820 82.57 20 2003.175 0.100 21 39.865 3.276 1.49782082.57 22 126.969 Variable 23 −93.904 1.200 1.651000 56.24 24 16.8563.445 1.850260 32.35 25 25.191 Variable 26 35.428 1.200 1.846660 23.8027 21.655 5.108 1.497820 82.57 28 −171.432 0.100 29 33.206 3.5381.497820 82.57 30 −872.482 0.100 31 39.698 3.189 1.497820 82.57 32−218.559 Variable 33 34.641 1.200 1.883000 40.66 34 17.547 4.063 35108.037 1.200 1.883000 40.66 36 17.905 2.721 1.846660 23.80 37 31.0295.953 38 −20.014 1.200 1.834810 42.73 39 −33.721 0.100 40 155.950 5.0371.805180 25.45 41 −26.603 5.976 42 −21.724 1.200 1.883000 40.66 43−91.209 0.100 44 42.254 4.806 1.497820 82.57 45 −300.388 BF Image plane∞ [Various Data] Variable magnification ratio 2.75 W M T f 71.4 140.0196.0 FNO 4.1 4.1 4.1 ω 17.1° 8.7° 6.20° Y 21.6 21.6 21.6 TL 219.219219.219 219.219 BF 37.319 37.319 37.319 <Infinite focusing state> W M Td5 1.000 28.185 36.224 d12 31.750 14.785 1.000 d15 11.220 1.000 6.746d22 2.609 2.609 2.609 d25 17.785 17.785 17.785 d32 1.000 1.000 1.000<Close distance focusing state (photographic distance 0.38 m)> W M T d51.000 28.185 36.224 d12 31.750 14.785 1.000 d15 11.220 1.000 6.746 d223.875 6.493 10.683 d25 15.253 10.018 1.637 d32 2.266 4.883 9.073 [LensGroup data] Group Starting surface f 1 1 106.207 2 6 −31.224 3 13 93.7674 16 115.857 [Values for Conditional Expressions] (1-1) |fvr|/f4 = 0.42(1-2) (−fn)/f4 = 0.30 (1-3) fp/f4 = 0.22 (1-4) D/D4 = 0.22 (2-1) fp/f4 =0.22 (2-2) (−fn)/f4 = 0.30 (2-3) |fvr|/f4 = 0.42 (2-4) D/D4 = 0.22

FIGS. 6A and 6B are graphs showing various aberrations of the variablemagnification optical system according to the second Example of thepresent application in a wide-angle end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 6C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIGS. 7A and 7B are graphs showing various aberrations of the variablemagnification optical system according to the second Example of thepresent application in an intermediate focal length state, upon focusingon an infinitely distant object, and upon focusing on a close distanceobject, respectively, and FIG. 7C is a graph showing a coma aberrationof the variable magnification optical system when the vibrationreduction is conducted upon focusing on an infinitely distant object.

FIGS. 8A and 8B are graphs showing various aberrations of the variablemagnification optical system according to the second Example of thepresent application in a telephoto end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 8C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

As is seen from the aberration graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance over the range from the wide-angle end state to thetelephoto end state and exhibits excellent optical performance also whenthe vibration reduction is conducted.

Third Example

FIG. 9 shows a sectional view of a variable magnification optical systemin a wide-angle end state according to a third Example common to thefirst and the second Embodiments of the present application.

The variable magnification optical system according to the presentexample is composed of, in order from the object side, a first lensgroup G1 having positive refractive power, a second lens group G2 havingnegative refractive power, a third lens group G3 having positiverefractive power, and a fourth lens group G4 having positive refractivepower.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L101 having aconvex surface facing the object side cemented with a double convexpositive lens L102, and a positive meniscus lens L103 having a convexsurface facing the object side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L201 having a convex surface facing the objectside, a cemented lens constructed by a double concave negative lens L202cemented with a positive meniscus lens L203 having a convex surfacefacing the object side, and a negative meniscus lens L204 having aconvex surface facing the image side.

The third lens group G3 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L301 having aconvex surface facing the object side cemented with a double convexpositive lens L302.

The fourth lens group G4 consists of, in order from the object side, afirst fixed lens group G41 having positive refractive power, a focusinglens group GF having positive refractive power, and a second fixed lensgroup G42 having negative refractive power.

The first fixed lens group G41 consists of, in order from the objectside, a double convex positive lens L401, an aperture stop S, a positivemeniscus lens L402 having a convex surface facing the object side, and apositive meniscus lens L403 having a convex surface facing the objectside.

The focusing lens group GF consists of, in order from the object side, afirst focusing group GN having negative refractive power and a secondfocusing group GP having positive refractive power.

The first focusing group GN consists of, in order from the object side,a cemented lens constructed by a double concave negative lens L404cemented with a positive meniscus lens L405 having a convex surfacefacing the object side.

The second focusing group GP consists of, in order from the object side,a cemented lens constructed by a negative meniscus lens L406 having aconvex surface facing the object side cemented with a double convexpositive lens L407, a double convex positive lens L408, and a doubleconvex positive lens L409.

The second fixed lens group G42 consists of, in order from the objectside, a negative meniscus lens L410 having a convex surface facing theobject side, a vibration reduction lens group GVR having negativerefractive power, a negative meniscus lens L413 having a convex surfacefacing the image side, a double convex positive lens L414, a negativemeniscus lens L415 having a convex surface facing the image side, and apositive meniscus lens L416 having a convex surface facing the objectside.

The vibration reduction lens group GVR consists of, in order from theobject side, a cemented lens constructed by a negative meniscus lensL411 having a convex surface facing the object side cemented with apositive meniscus lens L412 having a convex surface facing the objectside.

In the variable magnification optical system according to the presentexample with the above configuration, upon zooming from a wide-angle endstate to a telephoto end state, the second lens group G2 and the thirdlens group G3 are moved toward the image side along the optical axissuch that an air distance between the first lens group G1 and the secondlens group G2 is increased, an air distance between the second lensgroup G2 and the third lens group G3 is varied, and an air distancebetween the third lens group G3 and the fourth lens group G4 is varied.At that time, the first lens group G1 and the fourth lens group G4 arefixed for their positions.

In the variable magnification optical system according to the presentexample, the first focusing group GN in the fourth lens group G4 ismoved along the optical axis toward the image side and the secondfocusing group GP is moved along the optical axis toward the object sideto thereby conduct focusing from an infinitely distance object to aclose distance object.

Also, in the variable magnification optical system according to thepresent example, the vibration reduction lens group GVR in the fourthlens group G4 is moved so as to contain a component in a directionperpendicular to the optical axis to thereby conduct the vibrationreduction.

Values of specifications for the variable magnification optical systemaccording to the present example are shown in Table 3 given below.

TABLE 3 Third Example [Surface Data] Surface number r d nd νd Objectsurface ∞  1 83.2391 1.200 1.805180 25.45  2 62.0687 11.453  1.43384895.23  3 −651.7790 0.100  4 65.4552 7.206 1.433848 95.23  5 253.2044Variable  6 95.5535 1.200 1.883000 40.66  7 29.5434 5.992  8 −86.36951.200 1.497820 82.57  9 31.7368 5.301 1.846660 23.80 10 578.5867 18.487 11 −40.7518 1.200 1.902000 25.26 12 −74.2042 Variable 13 102.8697 1.2001.950000 29.37 14 43.1725 4.960 1.670030 47.14 15 −89.2434 Variable 16204.9923 2.866 1.497820 82.57 17 −121.8504 0.100 18(Stop S) ∞ 0.100 1968.7782 2.974 1.497820 82.57 20 3503.5297 0.100 21 39.1139 3.2911.497820 82.57 22 123.1531 Variable 23 −98.9742 1.200 1.651600 58.57 2416.6522 3.495 1.834000 37.18 25 24.9923 Variable 26 35.1436 1.2001.846660 23.80 27 21.9360 5.242 1.497820 82.57 28 −240.8524 0.100 2933.8985 3.887 1.497820 82.57 30 −250.0536 0.155 31 48.2044 3.2321.497820 82.57 32 −221.4035 Variable 33 34.8138 1.200 1.883000 40.66 3418.4001 4.275 35 136.9381 1.200 1.883000 40.66 36 19.0438 2.715 1.84666023.80 37 31.9873 6.398 38 −20.0907 1.200 1.834810 42.73 39 −31.88480.100 40 154.9619 5.445 1.805180 25.45 41 −26.2808 5.267 42 −21.46081.200 1.883000 40.66 43 −85.6881 0.100 44 41.2616 4.655 1.497820 82.5745 74612.0510 BF Image plane ∞ [Various Data] Variable magnificationratio 2.46 W M T f 72.0 100.0 177.0 FNO 4.1 4.1 4.1 ω 16.9° 12.2° 6.9° Y21.6 21.6 21.6 TL 219.219 219.219 219.219 BF 37.319 37.319 37.319<Infinite focusing state> W M T d5 1.000 16.852 34.493 d12 28.834 21.3901.000 d15 10.397 1.988 4.737 d22 2.595 2.595 2.595 d25 16.869 16.86916.869 d32 1.000 1.000 1.000 <Close distance focusing state(photographic distance 0.35 m)> W M T d5 1.000 16.853 34.493 d12 28.83421.390 1.000 d15 10.397 1.988 4.737 d22 4.171 5.202 10.453 d25 13.71711.654 1.151 d32 2.576 3.607 8.858 [Lens Group data Group f 1 108.723 2−32.794 3 98.135 4 115.860 [Values for Conditional Expressions] (1-1)|fvr|/f4 = 0.40 (1-2) (−fn)/f4 = 0.30 (1-3) fp/f4 = 0.23 (1-4) D/D4 =0.21 (2-1) fp/f4 = 0.23 (2-2) (−fn)/f4 = 0.30 (2-3) |fvr|/f4 = 0.40(2-4) D/D4 = 0.21

FIGS. 10A and 10B are graphs showing various aberrations of the variablemagnification optical system according to the third Example of thepresent application in a wide-angle end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 10C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

FIGS. 11A and 11B are graphs showing various aberrations of the variablemagnification optical system according to the third Example of thepresent application in an intermediate focal length state, upon focusingon an infinitely distant object, and upon focusing on a close distanceobject, respectively, and FIG. 11C is a graph showing a coma aberrationof the variable magnification optical system when the vibrationreduction is conducted upon focusing on an infinitely distant object.

FIGS. 12A and 12B are graphs showing various aberrations of the variablemagnification optical system according to the third Example of thepresent application in a telephoto end state, upon focusing on aninfinitely distant object, and upon focusing on a close distance object,respectively, and FIG. 12C is a graph showing a coma aberration of thevariable magnification optical system when the vibration reduction isconducted upon focusing on an infinitely distant object.

As is seen from the aberration graphs, the variable magnificationoptical system according to the present example shows superb opticalperformance over the range from the wide-angle end state to thetelephoto end state and exhibits excellent optical performance also whenthe vibration reduction is conducted.

According to each of the Examples, variable magnification opticalsystems can be realized which have higher optical performance whileexhibiting the vibration reduction function. Furthermore, the aboveExamples are a concrete example of the present invention, and theinvention is not restricted to the Examples. The contents given belowcan be arbitrarily adopted so far as the optical performance of thevariable magnification optical systems according to the first and thesecond Embodiments of the present application is not deteriorated.

Although the variable magnification optical systems each having afour-group configuration have been described above as numerical Examplesof such variable magnification optical systems according to the firstand the second Embodiments, the present application is not limited tothem, and a variable magnification optical system having otherconfigurations (such as, for example, five- or six-group configuration)can be constructed. Specifically, the variable magnification opticalsystems according to the first and the second Embodiments of the presentapplication may have such a lens configuration that a lens or a lensgroup is added to the most object side or the most image side of theoptical system.

Also, in the variable magnification optical systems according to thefirst and the second Embodiments of the present application, in order tovary focusing from an infinitely distant object to a close distantobject, a part of the lens group, a single lens group in the entiretythereof, or a plurality of the lens groups may be constructed so as tobe moved along the optical axis as a focusing lens group. In particular,it is preferable that at least a part of the fourth lens group is usedas the focusing lens group. The focusing lens group can be applied to anauto focus and is suitable for being driven by a motor for autofocusing, such as an ultrasonic motor.

Further, the variable magnification optical systems according to thefirst and the second Embodiments of the present application may beconstructed such that any lens group in its entirety, or a part thereofmay be used as a vibration reduction lens group and moved so as tocontain a component in the direction perpendicular to the optical axisor rotationally moved in an intra-plane direction including the opticalaxis (swayed), thereby conducting the vibration reduction. Inparticular, it is preferable that, in the variable magnification opticalsystems according to the first and the second Embodiments of the presentapplication, at least a part of the fourth lens group is used as thevibration reduction lens group.

Also, in the variable magnification optical systems according to thefirst and the second Embodiments of the present application, a lenssurface of the constitutional lenses may be made spherical, plane oraspherical. When the lens surface is a spherical surface or a planesurface, it is preferable because lens processing, assembling andadjustment become easy, and the optical performance can be preventedfrom being deteriorated by errors in the lens processing, assembling andadjustment. Also, it is preferable because even if the image plane isshifted, the deterioration in the optical performance is very little.When the lens surface is an aspherical surface, the aspherical surfacemay be formed by a grinding process, a glass molding process in which aglass material is formed into an aspherical shape using a mold, or acompound type process in which a resin material on a glass surface isformed into an aspherical shape. Also, the lens surface may be adiffractive optical surface, and the lens may be a gradient index lens(GRIN lens) or a plastic lens.

Also, it is preferable that, in the variable magnification opticalsystems according to the first and the second Embodiments of the presentapplication, the aperture stop is disposed in the fourth lens group, andits role may be substituted by the frame of the lens without providing aconstituent member as the aperture stop.

Moreover, the lens surface of the lenses constituting the variablemagnification optical systems according to the first and the secondEmbodiments of the present application may be applied with ananti-reflection coating having a high transmittance in a broad range ofwavelength. With this contrivance, it is feasible to reduce a flare aswell as ghost and achieve higher contrast and higher opticalperformance.

Also, the variable magnification optical systems according to the firstand the second Embodiments of the present application has a 35 mmequivalent focal length of about 60 to 80 mm in the wide-angle end stateand a 35 mm equivalent focal length of about 150 to 200 mm in thetelephoto end state. Additionally, the variable magnification opticalsystems according to the first and the second Embodiments of the presentapplication have a variable magnification ratio of on the order of 1.5to 4. Furthermore, in the variable magnification optical systemsaccording to the first and the second Embodiments of the presentapplication, a maximum shooting magnification beta β in any focal lengthstate is equal to or exceeds −0.5 or equal to or falls below −1.0, andas a result, both of the close distance photographing and the variablemagnification can be achieved simultaneously.

Next, a camera equipped with a variable magnification optical systemaccording to the first and the second Embodiments of the presentapplication will be described with referring to FIG. 13.

FIG. 13 is a view showing a configuration of a camera equipped with avariable magnification optical system according to the first and thesecond Embodiments of the present application.

The present camera 1 is an interchangeable lens, single-lens reflexdigital camera equipped with the variable magnification optical systemaccording to the above first Example as an imaging lens 2.

In the present camera 1, light emitted from an unillustrated object (anobject to be photographed) is converged by the imaging lens 2, reflectedby a quick return mirror 3, and focused on a focusing screen 4. Thelight focused on the focusing screen 4 is reflected a plurality of timesin a pentagonal roof prism 5, and is led to an eyepiece 6. Accordingly,a photographer can observe the object image as an erected image throughthe eyepiece 6.

When the photographer presses an unillustrated release button down, thequick return mirror 3 is retracted from the optical path, and the lightfrom the unillustrated object forms an object image on an imaging device7. Accordingly, the light emitted from the object is captured by theimaging device 7, and stored in an unillustrated memory as aphotographed image of the object. In this manner, the photographer cantake a picture of an object by the camera 1.

Here, the variable magnification optical system according to the abovefirst Example installed as the imaging lens 2 in the camera 1 has higheroptical performance while exhibiting the vibration reduction function asmentioned above. In other words, the present camera 1 can realize higheroptical performance together with the vibration reduction function.Incidentally, even if a variable magnification optical system accordingto the second and the third Examples is installed as an imaging lens 2in a camera, the same effect as the camera 1 can be obtained. Further,even if the variable magnification optical system according to each ofthe above Examples is installed in a camera, which does not include aquick return mirror 3, the same effect as the above described camera 1can be obtained.

Lastly, an outline of a method for manufacturing the variablemagnification optical systems according to the first and the secondEmbodiments of the present application is described with reference toFIGS. 14 and 15.

FIG. 14 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system according to the firstEmbodiment of the present application.

The method for manufacturing the variable magnification optical systemaccording to the first Embodiment of the present application shown inFIG. 14 is a method for manufacturing a variable magnification opticalsystem comprising, in order from an object side, a first lens grouphaving positive refractive power, a second lens group having negativerefractive power, a third lens group having positive refractive power,and a fourth lens group having positive refractive power, and the methodcomprises the following steps of S11 and S12:

Step S11: Preparing a first to a fourth lens groups and disposing thelens groups in a lens barrel in order from an object side, and thenproviding the lens barrel with a known movement mechanism to therebyconfigure the lens group such that, upon zooming, a distance between theadjacent lens groups is varied and the position of the first lens groupis fixed.

Step S12: Providing the lens barrel with a known movement mechanism tothereby construct the fourth lens group so as to comprise a vibrationreduction lens group which is moved so as to have a component in adirection perpendicular to the optical axis as well as a focusing lensgroup which is moved along the optical axis upon focusing.

Thus, the method for manufacturing a variable magnification opticalsystem according to the first Embodiment of the present applicationmakes it possible to manufacture a variable magnification optical systemhaving higher optical performance while exhibiting the vibrationreduction function.

FIG. 15 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system according to the secondEmbodiment of the present application.

The method for manufacturing the variable magnification optical systemaccording to the second Embodiment of the present invention shown inFIG. 15 is a method for manufacturing a variable magnification opticalsystem comprising, in order from an object side, a first lens grouphaving positive refractive power, a second lens group having negativerefractive power, a third lens group having positive refractive power,and a fourth lens group having positive refractive power, and the methodcomprises the following steps of S21 to S24:

Step S21: Preparing a first to a fourth lens groups and disposing thelens groups in a lens barrel in order from an object side, and thenproviding the lens barrel with a known movement mechanism to therebyconfigure the lens group such that, upon zooming, a distance between theadjacent lens groups is varied and the position of the first lens groupis fixed.

Step S22: Providing the lens barrel with a known movement mechanism tothereby construct the fourth lens group so as to comprise a focusinglens group which is moved along the optical axis upon focusing.

Step S23: Constructing the focusing lens group so as to comprise, inorder from an object side, a first focusing group having negativerefractive power and a second focusing group having positive refractivepower.

Step S24: Constructing the variable magnification optical system so asto satisfy the following conditional expression (2-1):

0.10<fp/f4<0.45  (2-1)

where fp denotes a focal length of the second focusing group; and f4denotes a focal length of the fourth lens group.

Thus, the method for manufacturing a variable magnification opticalsystem according to the second Embodiment of the present applicationmakes it possible to manufacture a variable magnification optical systemhaving higher optical performance.

1. A variable magnification optical system comprising, in order from anobject side along an optical axis: a first lens group having positiverefractive power, and an image side lens group disposed to an image sideof the first lens group, upon zooming, at least a distance between thefirst lens group and the image side lens group being varied, the imageside lens group comprising a focusing lens group which is moved alongthe optical axis upon focusing.
 2. A variable magnification opticalsystem comprising, in order from an object side along an optical axis: afirst lens group having positive refractive power, and an image sidelens group disposed to an image side of the first lens group, uponzooming, at least a distance between the first lens group and the imageside lens group being varied, the image side lens group comprising afocusing lens group which is moved along the optical axis upon focusing,the focusing lens group comprising, in order from the object side, afirst focusing group and a second focusing group, and the followingconditional expression being satisfied:0.10<|fp|/f4<0.45 where fp denotes a focal length of the second focusinggroup, and f4 denotes a focal length of the image side lens group. 3.The variable magnification optical system according to claim 1 wherein,upon zooming, the first lens group is fixed in position.
 4. The variablemagnification optical system according to claim 1, wherein the focusinglens group comprises a first focusing group having negative refractivepower and a second focusing group having positive refractive power, andupon focusing, a distance between the first focusing group and thesecond focusing group is varied.
 5. The variable magnification opticalsystem according to claim 1, wherein the focusing lens group comprises afirst focusing group and a second focusing group, and upon focusing froman infinitely distant object to a close distant object, the firstfocusing group is moved away from the object side along the opticalaxis, and the second focusing group is moved toward the object sidealong the optical axis.
 6. The variable magnification optical systemaccording to claim 1, wherein the focusing lens group comprises a firstfocusing group having negative refractive power and a second focusinggroup, and the following conditional expression is satisfied:0.20<(−fn)/f4<0.60 where fn denotes a focal length of the first focusinggroup, and f4 denotes a focal length of the image side lens group. 7.The variable magnification optical system according to claim 1, whereinthe image side lens group comprises a vibration reduction lens groupwhich is movable with a movement component in a direction perpendicularto the optical axis.
 8. The variable magnification optical systemaccording to claim 1, wherein the image side lens group comprises avibration reduction lens group which is movable with a movementcomponent in a direction perpendicular to the optical axis, and thefollowing conditional expression is satisfied:0.10<|fvr|/f4<0.80 where fvr denotes a focal length of the vibrationreduction lens group, and f4 denotes a focal length of the image sidelens group.
 9. The variable magnification optical system according toclaim 1, wherein the focusing lens group comprises a first focusinggroup and a second focusing group, and the following conditionalexpression is satisfied:0.12<D/D4<0.40 where D denotes a distance between the first focusinggroup and the second focusing group upon focusing on an infinitelydistant object, and D4 denotes a length on the optical axis of the imageside lens group.
 10. The variable magnification optical system accordingto claim 1, wherein the image side lens group is a lens group disposedat the most image side, and upon zooming, a distance between the lensesincluded in the image side lens group is not varied.
 11. The variablemagnification optical system according to claim 1, wherein the systemcomprises, in order from the object side, the first lens group, a secondlens group having negative refractive power, a third lens group havingpositive refractive power, and the image side lens group.
 12. An opticalapparatus equipped with the variable magnification optical systemaccording to claim
 1. 13. A method for manufacturing a variablemagnification optical system comprising, in order from an object sidealong an optical axis, a first lens group having positive refractivepower, a second lens group having negative refractive power, a thirdlens group having positive refractive power and a fourth lens grouphaving positive refractive power, the method comprising: arranging thelens groups such that, upon zooming, a distance between adjacent lensgroups is varied; constructing the fourth lens group to comprise afocusing lens group which is moved along the optical axis upon focusing;and constructing such that a shooting magnification is any focal lengthstate is equal to or exceeds −0.5.
 14. A method for manufacturing avariable magnification optical system comprising, in order from anobject side along an optical axis, a first lens group having positiverefractive power, a second lens group having negative refractive power,a third lens group having positive refractive power and a fourth lensgroup having positive refractive power, the method comprising: arrangingthe lens groups such that, upon zooming, a distance between adjacentlens groups is varied; constructing the fourth lens group to comprise afocusing lens group which is moved along the optical axis upon focusing;constructing the focusing lens group to comprise, in order from theobject side, a first focusing group having negative refractive power anda second focusing group having positive refractive power; constructingsuch that a shooting magnification in any focal length state is equal toor exceeds −0.5; and satisfying the following conditional expression:0.10<fp/f4<0.45 where fp denotes a focal length of the second focusinggroup, and f4 denotes a focal length of the fourth lens group.
 15. Thevariable magnification optical system according to claim 1, wherein ashooting magnification in any focal length state is equal to or exceeds−0.5.
 16. The variable magnification optical system according to claim2, wherein, upon zooming, the first lens group is fixed in position. 17.The variable magnification optical system according to claim 2, whereinthe first focusing group has negative refractive power and the secondfocusing group has positive refractive power, and upon focusing, adistance between the first focusing group and the second focusing groupis varied.
 18. The variable magnification optical system according toclaim 2, wherein upon focusing from an infinitely distant object to aclose distant object, the first focusing group is moved away from theobject side along the optical axis, and the second focusing group ismoved toward the object side along the optical axis.
 19. The variablemagnification optical system according to claim 2, wherein the firstfocusing group has negative refractive power, and the followingconditional expression is satisfied:0.20<(−fn)/f4<0.60 where fn denotes a focal length of the first focusinggroup, and f4 denotes a focal length of the image side lens group. 20.The variable magnification optical system according to claim 2, whereinthe image side lens group comprises a vibration reduction lens groupwhich is movable with a movement component in a direction perpendicularto the optical axis.
 21. The variable magnification optical systemaccording to claim 2, wherein the image side lens group comprises avibration reduction lens group which is movable with a movementcomponent in a direction perpendicular to the optical axis, and thefollowing conditional expression is satisfied:0.10<|fvr|/f4<0.80 where fvr denotes a focal length of the vibrationreduction lens group, and f4 denotes a focal length of the image sidelens group.
 22. The variable magnification optical system according toclaim 2, wherein the following conditional expression is satisfied:0.12<D/D4<0.40 where D denotes a distance between the first focusinggroup and the second focusing group upon focusing on an infinitelydistant object, and D4 denotes a length on the optical axis of the imageside lens group.
 23. The variable magnification optical system accordingto claim 2, wherein the image side lens group is a lens group disposedat the most image side, and upon zooming, a distance between the lensesincluded in the image side lens group is not varied.
 24. The variablemagnification optical system according to claim 2, wherein the systemcomprises, in order from an object side, the first lens group, a secondlens group having negative refractive power, a third lens group havingpositive refractive power, and the image side lens group.
 25. An opticalapparatus equipped with the variable magnification optical systemaccording to claim
 2. 26. The variable magnification optical systemaccording to claim 2, wherein a shooting magnification in any focallength state is equal to or exceeds −0.5.